First record of Maja squinado (Herbst, 1788) (Decapoda, Brachyura, Majidae) from the Pliocene of Masserano, Biella (Piemonte, NW Italy)

2009·4.3 MB·

by  Giovanni Pasini

Atti Soc. it. Sci. nat. Museo civ. Stor. nat. Milano, 150 (I): 13-20, Gennaio 2009
Giovanni Pasini’ & Alessandro Garassino”
First record of Maja squinado (Herbst, 1788)
(Decapoda, Brachyura, Majidae) from thè Pliocene
of Masserano, Biella (Piemonte, NW Italy)
Abstract - The record of Maja squinado (Herbst, 1788) (Majidae Samouelle, 1819) from thè
Pliocene of Masserano, Biella (NW Italy) is thè first for this family in Piemonte. The discovery incre-
ases thè knowledge of thè carcinologie assemblage in thè area and documents a wider geographical
distribution of thè species in thè Pliocene. Maja squinado (Herbst, 1788) was previously reported from
thè Pliocene of Emilia Romagna, Lazio, Puglia and Sardegna. Moreover, its presence in thè NW of thè
Mediterranean Sea (Paleo-Adriatic Basin) also indicates thè northem limit of its spread into thè old
Pliocene padanian Gulf.
Key words: Decapoda, Brachyura, Majidae, Pliocene, Italy.
Riassunto - Prima segnalazione di Maja squinado (Herbst, 1788) (Decapoda, Brachyura, Maji¬
dae) nel Pliocene di Masserano, Biella (Italia nord-occidentale).
La scoperta di Maja squinado (Herbst, 1788) (Majidae Samouelle, 1819) nel Pliocene di Masse¬
rano, Biella (Italia nord-occidentale) è la prima segnalazione della famiglia nel bacino piemontese,
che non solo incrementa le conoscenze carcinologiche dell'area, ma amplia anche la distribuzione
geografica della specie nel Pliocene. M. squinado (Herbst, 1788) è stata precedentemente segnalata nel
Pliocene delTEmilia Romagna, Lazio, Puglia e Sardegna. La sua presenza nel NO del Mediterraneo
(Bacino Paleo-Adriatico) rappresenta il limite più settentrionale di diffusione della specie alLintemo
dell’antico golfo Pliocenico padano.
Parole chiave: Decapodi, Brachyura, Majidae, Pliocene, Italia.
Introduction and geological setting
Recently, Garassino et al. (2004) recorded thè presence of brachyurans and
anomurans from several localities of thè Cenozoic of Piemonte (NW Italy). In
this study thè following brachyurans were reported, Calappa granulata Linnaeus,
1758, Iìiapliocenica Ristori, 1819, Eriphia sp. as well as one anomuran, Pagurus
sp., from thè Pliocene of Masserano (Biella) (Fig. 1).
‘Museo Civico dei Fossili di Besano, Via Prestini 5, 21050 Besano (Varese), Italy,
e-mail: [email protected]
" Museo Civico di Storia Naturale, Corso Venezia 55, 20121 Milano, Italy,
e-mail: [email protected]
14 GIOVANNI PASINI & ALESSANDRO GARASSINO
Fig. 1 - Map of thè Piemonte with thè fossihferous locality (*). / Regione Piemonte, con la località
fossilifera (*).
The new record of Maja squinado (Herbst, 1788) increases thè faunal assem-
blage of this area, enlarging thè carcinological record from thè Cenozoic of Pie¬
monte. The Pliocene levels of Masserano also preserve a very rich and well docu-
mented malacological fauna, in addition to echinoderms and rare teeth of teleostean
and chondrichtyan fìshes (Pasini & Garassino, 2006).
The fossiliferous levels crop out along thè eroded banks of thè Osteria River.
These levels consist of more or less compact coarse sands and grey siltstone-mica-
ceous sands, altemating with arenaceous levels of Pliocene age, 4 meters thick
(Garassino et al., 2004).
The studied specimen Comes from a level of compact micaceous siltstone, with
associated disarticulate pelecypod mollusc shells and gastropod casts.
Previous reports of Maja squinado in Italy
Maja squinado (Herbst, 1788) was previously reported from thè Pliocene of
Arda River, (Piacenza, Emilia Romagna), Monte Mario, Farnesina (Roma, Lazio),
Rocca Vecchia (Lecce, Puglia), and Alghero (Sardegna) (Meneghini, 1857; Ristori,
1891; Varola, 1981; Garassino & De Angeli, 2004; De Angeli & Garassino, 2006)
(Fig. 2). Gemmellaro (1914) reported this species from thè younger levels of thè
Pleistocene of Monte Pellegrino (Palermo, Sicilia).
FIRST RECORD OF MAJA SQU1NADO FROM THE PLIOCENE OF MASSERANO, BIELLA (PIEMONTE, NW ITALY)
Fig. 2 - Paleogeographic reconstruction of Italy in thè Pliocene, with thè fossiliferous localities of M.
squinado (Herbst, 1778) (in grey lands above sea level) (modifìed, by Pinna, 1976). / Ricostruzione
paleogeografia dell'Italia durante il Pliocene con le località di rinvenimento di M. squinado (Flerbst,
1778) (in grigio le terre emerse) (modificata, da Pinna, 1976). 1) Masserano (Biella). 2) Arda River
(Piacenza). 3) Monte Mario, Farnesina (Roma). 4) Rocca Vecchia (Lecce). 5) Alghero (Sardegna).
Material
One incomplete carapace is preserved in a compact little block of hard siltstone also
including scattered moulds of shells belonging to different molluscs. The specimen is
preserved as a naturai three-dimensional cast with only small remains of thè originai
extemal cuticle. Originally thè specimen was partially covered by sediment and thè
preparation was made by air gravers, due to thè hard nature of thè surrounding rock.
16 GIOVANNI PASINI & ALESSANDRO GARASSINO
The specimen is housed in thè Paleontological Collections of thè Museo di
Storia Naturale di Milano (MSNM).
The measurements are expressed in millimetres.
The systematic palaeontology used in this paper follows thè recent classifica-
tion proposed by Martin & Davis (2001).
Systematic Palaeontology
Superfamily Majoidea Samouelle, 1819
Family Majidae Samouelle, 1819
Genus Maja Lamarck, 1801
Maja squinado (Herbst, 1788)
Figs. 3, 4
Type species: Cancer squinado Herbst, 1788, by originai designation.
Geological age: Pliocene.
Occurrence and measurements: Masserano, Biella (Piemonte, NW Italy).
One incomplete, well-preserved specimen in dorsal view.
MSNM Ì27212: length of carapace, 69; width of carapace, 70.
Fig. 3 - Maja squinado (Herbst, 1778), MSNM Ì27212 (x 1.2).
FIRST RECORD OF MAJA SQUINADO FROM THE PLIOCENE OF MASSERANO, BIELLA (PIEMONTE, NW ITALY)
Description. Carapace, nearly complete excluding thè frontal area, com-
pressed and broken in thè left posterior part, wide and more inflated posteriorly,
pear-shaped in outline, longer than wide (when complete). Smooth granulate and
spiny ornamentation on dorsal surface and fìve alternate main prominent spines
along each lateral margin, decreasing in size and length from anterior to middle
outline. Only fìrst left anterior postorbitai spine partially preserved in frontal
area. Anterior postorbitai spine stronger than lateral ones. Main spines slightly
divergent from axis and directed upward. Branchial regions developed and infla¬
ted, well marked by thè sinuous grooves, with a well developed centrai spine on
each side, ranged horizontally with thè 4th metagastric axial spine, similar in size.
Only three posterior axial spines preserved among originai fìve. Metagastric,
cardiac, and intestinal regions inflated, distinct and bulbous, with about-central
developed smooth spines located along longitudinal median axis. Pereiopods not
preserved except for fragmentary remains of P4, broken and located along latero-
posterior side of carapace. P4 straight and elongate with merus longer than other
elements.
Discussion. Even though thè specimen lacks thè frontal region, chelipeds and
almost all pereiopods, it shows many affìnities with thè morphology of Maja
Lamarck 1801, and thè peculiar characters of thè living species Maja squinado
(Herbst, 1788), as follows: piriform outline and size; forni, arrangement and
generai distribution of thè smooth spines and granulate tubercles of thè carapace
that is enlarged frontally and posteriorly but not distinctly humped; thè lateral
and thè fìve axial spines are smaller and are facing in different ways than that in
thè other fossil and Recent species.
Therefore, on thè basis of thè above-mentioned characters, thè studied spe¬
cimen has been assigned to M. squinado. Moreover thè evidence of a lateral
Fig. 4 - Comparison among thè carapace outlines of thè studied specimen and thè Recent species
of Maja living in thè Mediterranean Sea (different scales). / (Confronto fra i profili del carapace
dell’esemplare studiato e le specie viventi di Maja presenti nel Mediterraneo) (scale differenti). A)
MSNM Ì27212. B) M squinado. C) M. crispata. D) M. goltziana.
18 GIOVANNI PASINI & ALESSANDRO GARASSINO
branchial spine on either side of thè axial 4th may be explained as naturai intra-
specific variability or as related to thè growth stage in living forms (G. P., pers.
comm. 2008). However, thè lack of more complete specimens does not allow
more detailed discussion because thè above-mentioned character is visible just
on one single, incomplete specimen.
A further comparison was also made between thè fossil coeval specimen
(MG0603, housed in thè Museo Geologico di Castell’Arquato, Piacenza, see
Garassino & De Angeli, 2004) and with thè two other Recent species of thè genus,
M. crispata Risso, 1827, and M. goltziana d’Oliveira, 1888, that are widespread
in Mediterranean Sea. Both lack fossil records (Fig. 4). Maja crispata differs
from thè studied specimen in having stronger lateral spines, different tuberculate
ornamentation, a carapace with fìve slightly spiny axial bulbous tubercles, a shar-
per and more pointed frontal region, different outline form and humped carapace,
and a smaller body size in all growth stages. Maja goltziana differs in thè generai
distribution and development of ornamentation of thè humped carapace, with
very long and pointed lateral spines, fìve elongated and proversed axial spines
with two peculiar lateral ones on either side of thè 4th spine, that is longer than
thè others, and arranged to form a cross-like form with thè arms downward. The
frontal region is stretched, and thè body size is smaller, especially in adults spe¬
cimens (d’Oliveira, 1888).
Conclusion
Even though thè Recent M. squinado (Herbst, 1788) is considered today as
thè exclusive species widespread in thè Mediterranean Sea, present in thè distai
and inner sublittoral zone on sandy, detritic or rocky bottoms and ranged about
between 20 to 120 meters in depth, Maja is also represented by two other Medi¬
terranean species, M. crispata Risso, 1827 (= M. verrucosa H. Milne Edwards,
1834), living in thè north-east Atlantic between thè Biscay Gulf to thè western
Morocco and in thè Mediterranean Sea on soft and hard bottoms ranged from 0
to around 30 meters, and M. goltziana d’Oliveira, 1888, eurybathic species of
subtropical origin (d’Udekem d’Acoz, 1999), widespread in thè easthern Atlantic
from Portugal to West Africa and South Mediterranean Sea.
Until thè last century M. squinado was considered to be also distributed in
thè easthern Atlantic but today, thè similar larger Atlantic specimens are ascri-
bed to a different species, M. brachydactyla Balss, 1922, as confirmed by thè
review of all species of thè genus conducted by Neumann (1998), and Sotelo
et al. (2008)based on nonclinal morphological character differences of thè first
gonopods and multivariate analyses of morphometric measurements and genetic
study. Therefore on thè basis of these systematic evidences by Neumann (1988),
thè assignment of fossil specimens to M. squinado from thè Pliocene and Plei¬
stocene extra-Mediterranean area of North Europe (e.g. The Netherlands and
northern Belgium), as reported by Holthuis (1949) and van Bakel et al. (2003),
could be assigned to thè easthern Atlantic species or to different undescribed
species.
Finally, based upon thè nature of preservation, kind and size, thè studied spe¬
cimen could represent an alloctonous moulting stage (exuvia) belonging to a sub-
adult specimen. Moreover this fossil record indicates a widespread distribution of
thè species in all thè Mediterranean Sea from thè Pliocene.
FIRST RECORD OF MAJA SQUINADO FROM THE PLIOCENE OF MASSERANO, BIELLA (PIEMONTE, NW ITALY)
Aknowledgements
We wish to thank G. Teruzzi, Museo di Storia Naturale di Milano, to give us
thè permission to study thè specimen, discovered in an old invertebrate collec-
tion of Museo di Storia Naturale di Milano, A. De Angeli, “Amici del Museo G.
Zannato” Montecchio Maggiore (Vicenza) for thè useful suggestions, R. Cleva,
Muséum national d’Histoire naturelle, Paris, to give us thè permission to compare
thè specimens of Recent Mediterranean species, and R. M. Feldmann, Kent State
University, Ohio, for careful review and criticismi.
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Ricevuto: 21 aprile 2008
Approvato: 17 maggio 2008